Grade 11
  1. Basic concepts of chemistry  1.1. Importance of Chemistry  1.2. Nature and scope of chemistry  1.3. laws of chemical combination  1.3.1. Law of conservation of mass  1.3.2. Law of definite proportions  1.3.3. Law of multiple proportions  1.3.4. Law of gaseous volume  1.3.5. Avogadro's Law  1.4. Dalton's atomic theory  1.5. Mole concept and molar mass  1.6. Percent composition  1.7. Empirical and molecular formula  1.8. Stoichiometry and Stoichiometric Calculations  1.9. Limiting reagent concept
  2. Structure of the atom  2.1. Discovery of the electron, proton, and neutron  2.2. Atomic Model  2.2.1. Thomson's model  2.2.2. Rutherford's model  2.2.3. Bohr's model  2.3. Quantum mechanical model of the atom  2.4. Dual nature of matter and radiation  2.5. Heisenberg's uncertainty principle  2.6. Quantum numbers  2.7. Atomic orbitals and their shapes  2.8. Electronic configuration of elements  2.9. Aufbau principle  2.10. Pauli's exclusion principle  2.11. Hund's maximum multiplicity rule  2.12. de Broglie's hypothesis  2.13. Photoelectric effect
  3. Classification of elements and periodicity in properties  3.1. Historical development of the periodic table  3.2. Modern Periodic Law and Periodic Table  3.3. Periodic trends in properties  3.3.1. Atomic and Ionic Radius  3.3.2. Ionization enthalpy  3.3.3. Electron gain enthalpy  3.3.4. Electronegativity  3.3.5. Valency  3.3.6. Metallic and Non-Metallic Properties  3.3.7. Oxidation states  3.4. Unusual Properties of the First Elements
  4. Chemical Bonding and Molecular Structure  4.1. Kossel–Lewis approach to chemical bonding  4.2. Ionic or electrovalent bond  4.3. Covalent bond and its features  4.4. Bond parameters  4.5. VSEPR Theory  4.6. Valence bond theory  4.7. Hybridization and its types  4.8. Molecular orbital theory  4.8.1. Bond order and stability  4.9. Hydrogen bonding
  5. States of matter  5.1. Intermolecular forces  5.2. Gas Laws  5.2.1. Boyle's law  5.2.2. Charles's Law  5.2.3. Avogadro's Law  5.2.4. Dalton's law of partial pressure  5.2.5. Graham's law of spread  5.3. Ideal Gas Equation and Applications  5.4. Real gases and deviations from ideal behaviour  5.5. Kinetic molecular theory of gases  5.6. Liquefaction of gases  5.7. Properties of Liquids  5.8. Surface tension and viscosity
  6. Thermodynamics  6.1. System and environment  6.2. Types of systems in thermodynamics  6.3. Types of procedures  6.4. First law of thermodynamics  6.5. Internal energy and enthalpy  6.6. Heat capacity and specific heat  6.7. Hess's law of constant heat summation  6.8. Bond dissociation enthalpy  6.9. Enthalpy of formation and combustion  6.10. Enthalpy of solution and neutralization  6.11. Spontaneity and the second law of thermodynamics  6.12. Gibbs free energy and its applications
  7. Balance  7.1. The concept of balance  7.2. Equilibrium constant and its applications  7.3. Le Chatelier's principle  7.4. Ionic equilibrium in solutions  7.5. Acid and Base Theory  7.5.1. Arrhenius concept  7.5.2. Bronsted-Lowry concept  7.5.3. Lewis concept  7.6. pH Scale and pOH  7.7. Common ion effect  7.8. Hydrolysis of salts  7.9. Buffer solutions and their mechanism of action  7.10. Solubility equilibrium of sparingly soluble salts
  8. Redox reactions  8.1. Oxidation and reduction concepts  8.2. Oxidation number and its applications  8.3. Redox reactions in terms of electron transfer  8.4. Balancing redox reactions (oxidation number and ion-electron methods)  8.5. Types of redox reactions  8.6. Electrochemical Cells and Redox Reactions
  9. Hydrogen  9.1. Position of Hydrogen in the Periodic Table  9.2. Isotopes of hydrogen  9.3. Preparation of Hydrogen  9.4. Properties of Hydrogen  9.5. Hydrides and their classification  9.6. Water and heavy water  9.7. Hydrogen peroxide and its properties  9.8. Uses of Hydrogen and Its Compounds
  10. S-block elements (alkali and alkaline earth metals)  10.1. Group 1 Elements - Properties and Trends  10.2. Group 2 Elements - Properties and Trends  10.3. Unusual properties of lithium and beryllium  10.4. Important compounds of sodium and their uses  10.5. Important Compounds of Magnesium and Calcium
  11. Some p-block elements  11.1. General Introduction to p-Block Elements  11.2. Group 13 Elements  11.2.1. Boron and its compounds  11.3. Group 14 Elements  11.3.1. Carbon and its allotropes  11.3.2. Important Compounds of Carbon and Silicon
  12. Organic Chemistry - Some Basic Principles and Techniques  12.1. Classification and Nomenclature of Organic Compounds  12.2. Structural representation of organic compounds  12.3. Classification of organic reactions  12.4. Electronic Effects in Organic Chemistry  12.4.1. Inductive effect  12.4.2. Resonance effect  12.4.3. Hyperconjugation  12.5. Reaction mechanism and intermediate species  12.6. Purification and qualitative analysis of organic compounds
  13. Hydrocarbons  13.1. Hydrocarbons  13.1.1. Preparation and Properties of Alkenes  13.2. alkene  13.2.1. Preparation and Properties of Alkenes  13.2.2. Electrophilic addition reactions  13.3. Alkynes  13.3.1. Preparation and Properties of Alkynes  13.4. Aromatic hydrocarbons  13.4.1. Structure and properties of benzene  13.4.2. Electrophilic substitution reactions of benzene
  14. Environmental Chemistry  14.1. Environmental Pollution  14.2. Atmospheric pollution and the greenhouse effect  14.3. Water pollution and treatment methods  14.4. Soil pollution and its effects  14.5. Industrial waste and its treatment  14.6. Strategies for pollution control

Grade 11 → Hydrogen ↓


Hydrides and their classification


Hydrogen is the first and lightest element in the periodic table. It is a unique element, whose properties allow it to form compounds with almost every other element. These hydrogen compounds are known as hydrides. The study of hydrides is an essential part of chemistry, as these compounds are important both industrially and biologically.

The term "hydride" refers to a compound in which hydrogen is bonded to another element or group. Depending on the nature of the bond and the element combined with hydrogen, hydrides can be classified into different types. Understanding these classifications helps us predict the properties and reactivity of these compounds.

Classification of hydrides

Hydrides are broadly classified into three types:

  1. Molecular hydrides
  2. Ionic hydrides
  3. Metallic or interstitial hydrides

Molecular hydrides

Molecular hydrides, also called covalent hydrides, are formed when hydrogen forms covalent bonds with elements of similar or higher electronegativities. These are typically formed with non-metals, and the bond involves the sharing of electron pairs.

A common example of a molecular hydride is water (H 2 O). In water, each hydrogen atom shares one electron with an oxygen atom, forming a covalent bond. Below is a simplified electron-sharing diagram of water:

        H – O – H
Hey H H

Molecular hydrides can also be classified as electron-precise, electron-deficient, or electron-rich:

  • Electron-precise hydrides: These contain a sufficient number of bonds to satisfy the valency of the constituent atoms. For example, methane (CH 4) is electron-precise because it forms four covalent bonds with hydrogen.
  • Electron-deficient hydrides: These do not have enough electrons to form conventional covalent bonds. Borane (B 2 H 6) is an example of this, where the bonds are explained by three-center two-electron bonds, called banana bonds.
  • Electron rich hydrides: These contain extra pairs of electrons that do not participate in bonding, such as ammonia (NH 3).

Ionic hydrides

Ionic hydrides or saline hydrides are usually formed with metals, especially alkali metals and alkaline earth metals, which are highly electropositive. In these hydrides, the hydrogen atom gains an electron from the metal atom, forming a hydride ion H -.

Consider sodium hydride (NaH), an example of an ionic hydride. When sodium reacts with hydrogen, it transfers one electron to hydrogen, resulting in the sodium ion Na + and the hydride ion H -.

        Na + H → Na + + H -
Na + H -

Ionic hydrides are usually white crystalline solids. They are used in various chemical syntheses as a source of hydride ions and to transfer hydrogen in the form of hydride ions.

Metallic or interstitial hydrides

Metallic hydrides are formed when hydrogen interacts with transition metals. In these hydrides, the hydrogen atoms occupy interstitial sites within the metal lattice, i.e., the spaces between metal atoms. These are called interstitial hydrides.

Metallic hydrides often do not follow a simple stoichiometry, and their composition can vary. For example, titanium hydride and palladium hydride can absorb different amounts of hydrogen.

Metal atoms: grey squares, Hydrogen atoms: blue circles

Metallic hydrides, especially palladium hydrides, have fascinating properties, such as their ability to absorb and release hydrogen, making them useful for hydrogen storage solutions.

Applications of hydrides

Hydrides have various applications, which are influenced by their type and properties. Here are some examples:

  • Molecular Hydrides: Ammonia is used as a fertilizer and in the production of urea. Methane serves as an important energy source in natural gas.
  • Ionic hydrides: Sodium hydride is used as a drying agent and for deprotonation reactions in organic synthesis. Metal hydrides serve as reducing agents in metallurgical processes.
  • Metallic hydrides: These are important in hydrogen storage technologies, particularly as fuel cells and battery materials.

Reactivity of hydrides

The reactivity of hydrides varies widely depending on their classification:

  • Molecular hydrides: These can be relatively inert like methane or highly reactive like diborane. The presence of lone pairs in compounds like ammonia contributes to their basic and nucleophilic properties.
  • Ionic hydrides: These react vigorously with water, releasing hydrogen gas. For example, the reaction of sodium hydride with water: 
                    NaH + H 2 O → NaOH + H 2 ↑
  • Metallic hydrides: They often exhibit low reactivity due to the stability provided by the metal lattice. However, under the right conditions, they can release hydrogen gas.

Conclusion

Hydrides are a fascinating group of compounds with diverse structures and properties. Their classification into molecular, ionic and metallic hydrides helps us understand their unique behaviour and applications in various scientific and industrial fields. From energy storage to synthetic chemistry, hydrides provide important applications that are indispensable to modern science and technology.

As chemistry continues to develop, research on hydrides will expand and deepen, revealing more insights into sustainable energy solutions and advanced materials, making hydrides an exciting area of study for future chemists.


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Hydrides and their classification

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